Development of natural gas injection technology for NO sub x reduction from municipal waste combustors

Natural gas injection (NGI) technology for reducing NO{sub x} emissions from municipal waste combustors (MWCs) is being developed. The approach involves the injection of natural gas, together with recirculated flue gases (for mixing), above the grate to provide reducing combustion conditions that promote the destruction of NO{sub x} precursors, as well as NO{sub x}. Extensive development testing was subsequently carried out in a 2.5 {times} 10{sup 6} Btu/h (0.7 MWth) pilot-scale MWC firing actual MSW. Both tests, using simulated combustion products and actual MSW, showed that 50% to 70% NO{sub x} reduction could be achieved. These results were used to define the key operating parameters. A full-scale system has been designed and retrofitted to a 100-ton/day Riley/Takuma mass burn system at the Olmsted County Waste-to-Energy facility. The system was designed to provide variation in the key parameters to not only optimize the process for the Olmsted unit, but also to acquire design data for MWCs of other sizes and designs. Extensive testing was conducted to December 1990 and January 1991 to evaluate the effectiveness of NGI. This paper concentrates on the METHANE de-NO{sub x} system retrofit and testing. The results show simultaneous reductions of 60% in NO{sub x}, 50% inmore » CO, and 40% in excess air requirement with natural gas injection. 4 refs., 5 figs., 1 tab.« less